PROJECT 3: SUMMARY/ABSTRACT Many hazardous chemicals at Superfund sites have been linked to adverse health effects, but their toxicological mechanisms remain poorly understood. This project will apply innovative analytical technologies to dissect and simplify the complexities associated with analyzing the toxicological mechanisms associated with exposure to chemical mixtures and the Exposome. We have developed a chemical proteomic technology termed reactivity-based protein profiling (RBPP) that enables the mapping of direct interactions of reactive SRP chemicals with protein targets in complex biological systems. This is a novel and very innovative technology that enables a comprehensive assessment of how chemicals interact with specific molecular targets directly in complex mammalian physiology, which in-turn informs the types of downstream biochemical and pathological effects that may result from chemical exposure. This technology and the information revealed from using it will vastly expand our knowledge of: 1) novel toxicological mechanisms of individual SRP chemicals; 2) common pathways that may be targeted by multiple SRP chemicals; and 3) toxicological mechanisms that may arise from exposure to chemical mixtures and other factors in the Exposome. We hypothesize that dissecting out the individual targets of chemicals and mapping common pathways that are targeted across multiple chemicals will enable us to identify particularly important toxicological mechanisms associated exposure to complex chemical mixtures. We have been using RBPP to profile direct protein targets of many widely used environmental chemicals of concern. We have found that several protein targets involved in fatty acid degradation, metabolism, and steroidogenesis are directly and commonly inhibited by a strikingly large number of reactive environmental chemicals. These commonly targeted pathways are likely to result in adverse health effects since inhibiting the burning of fat will lead to accumulation of fat in tissues and inhibiting steroid hormone degradation will lead to accumulation in both hormones like testosterone and cortisol which may have behavioral and tumor promoting effects. We hypothesize that cumulative exposure to these reactive SRP chemicals and the inhibition of protein targets involved in fat and steroid metabolism will directly impact lipid and steroid levels in vivo in mice and humans. We propose to apply innovative analytical platforms to map proteome-wide targets of reactive SRP chemicals to reveal novel toxicological mechanisms with a particular focus on understanding how exposure to SRP chemical mixtures may synergize to impact fat and steroid metabolism. This project will directly address Problems 1, 3, and 4 on addressing the problem of: 1) mixtures, 2) complexities of chemicals operating through unique and overlapping mechanisms, and 3) identifying risks associated with chemical exposure in vulnerable populations, through using our innovative RBPP methods to simplify our understanding of toxicological mechanisms underlying chemical mixtures.